In the related art, an image forming apparatus which forms an image on a recording medium (for example, sheet) as a printing target is known. The image forming apparatus forms a toner image in a transfer unit, and transfers the toner image onto a sheet which is supplied to the transfer unit. The sheet onto which the toner image is transferred is heated and pressurized using a fixing unit, and the toner image is fixed onto the sheet.
The fixing unit includes a fixing belt including a heat source, and a pressurizing roller which faces the fixing belt and which applies a pressure to a sheet. The fixing unit interposes a sheet between the fixing belt and the pressurizing roller, melts toner by applying heat and a pressure, and fixes a toner image onto the sheet.
Usually, a width of the fixing belt is larger than that of a sheet. For this reason, a contact region which comes into contact with a sheet is present at a center portion of the fixing belt, and a non-contact region which does not come into contact with a sheet is present at an end portion of the fixing belt. Accordingly, heat moves to a sheet at the center portion of the fixing belt in the axial direction, when the center portion comes into contact with the sheet. Meanwhile, heat rises at both end portions of the fixing belt in the axial direction, and temperature irregularity occurs in the fixing belt, since both end portions do not come into contact with a sheet.
When temperature irregularity occurs in the fixing belt, there is a concern that a fixing failure or abnormal heating may be caused, and the fixing belt itself, or peripheral members of the fixing belt may ignite, and may be damaged. In addition, in order to cool down a temperature of the non-contact region, it is necessary to stop a fixing operation.